Targets/Samples
This page discusses how to use targeting-related tags to recover targeting decisions.
If you are curious as to why your objects of interest were observed, you are in the right place! If you are attempting to do a detailed study mapping our stars to an underlying population, some of the information here will be useful. Still, you should also review the page on Selection Bias. If why your target or sample was observed is irrelevant to your science, then carry on! The philosophy of targeting is presented on Targeting Information.
How Targeting Choices are Communicated
Alogrithms
Targeting Files
BITMASKS
APOGEE2_TARGET1
, APOGEE2_TARGET2
, and APOGEE2_TARGET3
. The target bitmasks used for APOGEE-1 targets are APOGEE_TARGET1
and APOGEE_TARGET2
(and an unused one called APOGEE_TARGET3). The right-hand navigation bar has links to bitmask descriptions. The bits within the flags are not exactly aligned between the two generations of APOGEE.
Targets from APOGEE-1 will only have APOGEE1 flags and vice versa.
The tag TARGFLAGS
in the summary files is a string with a list of the target flags for a given object.
Summary File Tags
PROGRAMNAME
, FIELD
, TELESCOPE
, and SURVEY
tags available for each target in the summary files. These convey when or where the specific target was observed and its primary science program (see Targeting Information).
EXTRATARG
The EXTRATARG
tag is filled during the pipeline processing to flag specific items. This is a tag created for convenience and not a funamental targeting flag. Generally, EXTRATARG
helps to simplify idenficiation of key samples as a uniform flagging between APOGEE1 and APOGEE2.
If no bits in EXTRATARG
are set, then this star meets the criteria for the Main Red Star Sample. It may, however, also be a special target (e.g., selected using other non-main red star sample criteria). Note that having no bits set is distinct from having bit 0 set!
Bit Tag | Bit | Description |
---|---|---|
NOT_MAIN |
0 | Not part of the main red star sample |
COMMISSIONING |
1 | Data obtained during instrument commissioning. |
TELLURIC |
2 | Target selected for determining the telluric correction. |
APO1M |
3 | NMSU-1m observation |
DUPLICATE |
4 | Duplicate observation |
Dissecting the Main Red Star Sample
Stars in the main red star sample should all have APOGEE2_NORMAL_SAMPLE
set, which is apogee2_target1
bit 14.
Main Red Star Sample BitMasks
Selection Decision | Bits | Description | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Magnitude Bin
|
|
These bits indicate the $H$ mag limit used to select these stars within their respective structural component as described in. | ||||||||
Magnitude Bin
|
|
Unique to APOGEE-2. A modified bright limit indicates a star in a cohort with a bright limits of $H \ge 10$ mag rather than the standard $H \ge 7$ mag. MaNGA led fields have a brighter faint limit due to differences in dithering strategy. | ||||||||
$(J-K_{s})_{0}$ Bin
|
|
These bits indicate the (J-K$_{s}$)$_{0}$ dereddened color-selection used to select this star. | ||||||||
Dereddening Method apogee_target1 or apogee2_target1 |
|
These bits indicate how or if $E(J-K)_{0}$ was determined. Either IRAC and WISE photometry are used with the RJCE method. If no MIR data are available, then SFD is used or no dereddening is applied. See dereddened color-selection. The bits in apogee_target1 and apogee2_target1 are aligned. |
Halo Selection
Selection Decision | Bits | Description | ||||
---|---|---|---|---|---|---|
Wash+D Class apogee_target1 or apogee2_target1 |
|
These bits indicate the classification of the star using Wash+D photometry. | ||||
Wash+D Class apogee2_target1 |
|
Unique to APOGEE-2. This bit indicates that the star did not have a Wash+D classification. |
Human Readable Tags
Tag in Summary File | Options and Description | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
AK_TARG_METHOD Note: this refers to the targeting catalog. The summary catalogs may not be filled from the same input targeting catalog. Original targeting values are available in the targeting input files. Various WISE releases are documented here. |
|
||||||||||||||||
COMMISS |
Set to 1 for data taken during spectrograph commissioning. | ||||||||||||||||
TARGFLAGS |
Verbose/text form of target flags | ||||||||||||||||
SURVEY |
|
||||||||||||||||
Target Selection Mag-Color Ranges |
|
||||||||||||||||
WASH_DDO51_GIANT_FLAG |
Flagged as a giant for targeting purposes based on Washington/DDO51 photometry | ||||||||||||||||
WASH_DDO51_STAR_FLAG |
Flagged as a star for targeting purposes based on Washington/DDO51 photometry |
Potentially Useful Samples
External Calibration Stars
Mask & Bit | Meaning | Description |
---|---|---|
APOGEE2_TARGET2 bit 2 |
APOGEE2_STANDARD_STAR |
star with previous stellar parameters or chemical abundance measurements |
APOGEE_TARGET2 or APOGEE2_TARGET2 bit 3 |
APOGEE_RV_STANDARD or APOGEE2_RV_STANDARD |
star with previous radial velocity measurements |
APOGEE2_TARGET2 bit 13 |
APOGEE2_LITERATURE_CALIB |
overlap with high-resolution literature studies |
APOGEE2_TARGET2 bit 5 |
APOGEE2_EXTERNAL_CALIB |
generic flag for external survey calibration, see Overlap with other Surveys for more details |
APOGEE2_TARGET2 bit 22 |
APOGEE2_1M_TARGET |
Stars with $H \leq$ 7 mag observed with APOGEE-N instrument's fiber-link to NMSU's 1-meter telescope. Those stars in the calibration program have FEILD set to "calib." See Special Programs. |
Internal Calibration Stars
APOGEE2_INTERNAL_CALIB
in APOGEE2_TARGET2
bit 6.
A number of stars were unintentionally observed multiple times and processed independently. These sources can be identified using EXTRATARG
.
Overlap with other Surveys
APOGEE2_TARGET2
bit 5, 13, 14, 15, 16, 17, and/or 18, as described further below:
Mask & Bit | Meaning | Description |
---|---|---|
APOGEE_TARGET1 bit 30 |
APOGEE_SEGUE_OVERLAP |
Star selected for overlap with SEGUE observations. |
APOGEE2_TARGET2 bit 5 |
APOGEE2_EXTERNAL_CALIB |
General flag for external overlap. |
APOGEE2_TARGET2 bit 13 |
APOGEE2_LITERATURE_CALIB |
|
APOGEE2_TARGET2 bit 14 |
APOGEE2_GES_OVERLAP |
Targets intentionally common with the Gaia-ESO
survey |
APOGEE2_TARGET2 bit 15 |
APOGEE2_ARGOS_OVERLAP |
Targets intentionally common with the Abundances and Radial velocity Galactic Origins Survey (ARGOS); see Freeman et al. (2013) |
APOGEE2_TARGET2 bit 16 |
APOGEE2_GAIA_OVERLAP |
|
APOGEE2_TARGET2 bit 17 |
APOGEE2_GALAH_OVERLAP |
Targets intentionally common with the GALactic Archaeology with HERMES (GALAH); see Martell et al. (2016) |
APOGEE2_TARGET2 bit 18 |
APOGEE2_RAVE_OVERLAP |
Targets intentionally common with the RAdial Velocity Experiment (RAVE); see Steinmetz et al. (2006) |